Gate valve with improved seal assembly

ABSTRACT

A valve having a body member defining a chamber with first and second ports, and a closure member movable in the chamber over the first port between open and closed positions to control flow between the ports. A resilient seal is mounted on either the body member or the closure member to seal the valve by bearing against a mating face of the other member when the valve is closed. A backup element is slidably mounted in the valve chamber to provide continuous confinement for the seal as the closure member is moved away from the closed position toward the open position. The backup element fits against the mating face member when the valve is opened to define a substantially continuous smooth surface in sliding contact with the seal and against which the seal is compressed. The smooth surface formed by the mating face member and the backup element is broken only by a line joint or seam between the member and element, and the seal passes easily over this joint without distorting or tending to extrude. After the closure member has retracted toward the open position sufficiently to pass the seal over the joint so the seal now bears entirely on the backup member, the closure member is further drawn past the first port to permit flow through the valve.

United States Patent Rogers 5] Feb. 8, 1972 [54] GATE VALVE WITHIMPROVED SEAL ASSEMBLY [72] inventor: William A. Rogers, 746 West 28thStreet, San Pedro, Calif. 90731 [22] Filed: Dec. 30, 1970 [21] Appl.No.: 102,825

Related US. Application Data [62] Division of Ser. No. 793,790, Jan. 24,1969, Pat. No.

Primary Examiner-Amold Rosenthal Artomey-Christie, Parker & HaleABSTRACT A valve having a body member defining a chamber with first andsecond ports, and a closure member movable in the chamber over the firstport between open and closed positions to control flow between theports. A resilient seal is mounted on either the body member or theclosure member to seal the valve by bearing against a mating face of theother member when the valve is closed. A backup element is slidablymounted in the valve chamber to provide continuous confinement for theseal as the closure member is moved away from the closed position towardthe open position. The backup element fits against the mating facemember when the valve is opened to define a substantially continuoussmooth surface in sliding contact with the seal and against which theseal is compressed. The smooth surface formed by the mating face memberand the backup element is broken only by a line joint or seam betweenthe member and element, and the seal passes easily over this jointwithout distorting or tending to extrude. After the closure member hasretracted toward the open position sufficiently to pass the seal overthe joint so the seal now bears entirely on the backup member, theclosure member is further drawn past the first port to permit flowthrough the valve.

3 Claims, 14 Drawing Figures PATENIEUFEH e 012 'SNEEY l. 0? 5 I NVENTOR; 14 41/444 4 foam;

Arm/Fwy;

PATENTEHFEB 8 1972 3. 6&0500

sum 3 BF 5 PNEWEBFEB s @972 SHEET 5 OF 5 GATE VALVE WITH IMPROVED SEALASSEMBLY CROSS REFERENCE TO RELATED APPLICATION This is a division of mycopending application Ser. No. 793,790, filed Jan. 24, 1969, now US.Pat. No. 3,561,731.

BACKGROUND OF THE INVENTION A problem common to many different types ofvalves is to provide a tight long-life seal which prevents leakage flowwhen the valve is closed. The sealing arrangement should be dependableover many cycles of valve operation, and ideally should be economical tomanufacture and essentially simple and economical to maintain. Inconventional valves, sealing is accomplished by either a resilient seal(such as an O-ring, lobed ring, or similar elastomeric element) or byproviding a very close lapped fit between a movable closure member and abody member of the valve. Both of these approaches have deficiencieswhich prevent the achievement of the aforementioned design goals invalves intended for high-pressure service, or which are used indifficult applications such as controlling the flow of cryogenic fluids.

In a typical spool valve, for example, a piston is slidably mounted in abore defined by a body of the valve. Ports open into the bore, and thepiston moves over at least one of the ports to control flow through thevalve. The piston and valve are very precisely machined and lapped toprovide a fit which is sufficiently close that flow is essentiallyblocked when the piston covers the port. Wear of the moving parts,however, will eventually destroy the close fit to cause leakage, andthis wear is accelerated when the valve controls flow of fluids whichcontain abrasive impurities. In high-pressure applications, the valvebody may expand sufficiently to create leakage paths between the pistonand body. Another problem is that lapped valves are subject to seizingwhen subjected to temperature variations. Finally, lapped valves areexpensive to manufacture and maintain.

The problems inherent in a lapped piston valve can sometimes be solvedby using a relatively loose-fitting piston and providing an inexpensiveresilient seal to close the resulting annular space between the pistonand the bore-defining wall of the valve body. Such ring-shaped seals areavailable in a variety of different cross sections, and are seated in agroove (on the piston, for example) to bear against and be confined inthe groove by the opposed surface of the bore along which it slides. Aresilient seal offers good sealing and long life when it bears against asmooth and unbroken bore surface. Seal integrity, however, isjeopardized when the bore surface has a discontinuity such as atransverse port over which the seal must pass as the piston is movedbetween open and closed valve positions.

As the resilient seal is moved over the port, the confining or squeezingaction of the bore wall is lost, and the seal tends to distort andextrude into the bore wall discontinuity formed by the port. The sealmay also be pinched or abraded as the piston moves over the port, andthe resulting cutting or tearing can cause leakage and makes the sealless resistant to extrusion out of the groove into the discontinuity. Asa result of these problems, soft or resilient seals are not usable inmost high-pressure valves, and an expensive lapped valve must beselected.

The problem of cross section distortion arising from extrusion of theseal is especially severe in valves used to control flow of cryogenicfluids. The elastomeric materials from which resilient seals are formedtend to harden at very low temperatures, and the seal is then verysusceptible to cracking, tearing or breaking when subjected to even arelatively slight cross section distortion arising from extrusion into adiscontinuity in the seal-confining surface of the valve body.

The invention herein disclosed is an improved seal assembly whichovercomes the problems commonly encountered with resilient seals invalves and similar devices. The invention contemplates the use of abackup element which is movably mounted in the valve, and which mateswith a discontinuous seal-confining surface to define a substantiallycontinuous surface which bears on the seal and is broken by only aline-contact joint or seam into which the seal does not tend to extrude.The seal is thus maintained under constant squeeze for all positions ofthe valve piston or closure member, and cross section distortion arisingfrom seal extrusion is avoided. This valve design is simple andeconomical to manufacture, and provides low-maintenance long-lifeservice in difficult highpressure or cryogenic applications without theexpense of providing a lapped fit between moving members of the valve.Overhaul or repair normally involves only replacement of the soft orresilient seal, and is quickly and economically accomplished. Theextensive teardown, major component replacement, and machining needed tooverhaul a lapped fit valve is thus avoided.

SUMMARY OF THE INVENTION This invention relates to an improved gatevalve which includes a valve body member having a slot therein defininga chamber. A pair of aligned and spaced-apart ports open into oppositesides of the chamber. A plate forming a closure gate member is linearlyslidable in the body member slot between an open position in which fluidcan flow through the chamber between the ports, and a closed position inwhich the closure member is disposed between the ports to block flowtherebetween. The closure member is slidable transversely with respectto a direction of flow between the ports when the valve is open.

A resilient seal is mounted on one of the members to be in slidingcontact with the other member as the closure member is moved away fromthe open position. A backup element is slidably disposed in the chamber,and is arranged to move into abutment with said other member as theclosure member approaches the closed position. The backup element isconfigured to define in conjunction with said other member asubstantially continuous smooth surface in sliding contact with theseal, and against which the seal is compressed as the closure member ismoved from the closed position toward the open position.

Preferably, the gate valve includes a resilient means arranged to urgethe backup element toward a position in which the substantiallycontinuous smooth surface is defined. In one form, the backup element isa plate 'slidably fitted in a channel in said other member, the platehaving a lug extending therefrom to engage said one member and therebymove the backup element plate as the valve is opened. The resilient sealextends peripherally around the backup element plate and associatedresilient means when the valve is closed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a cross-sectional elevationof a piston valve with a moving seal and backup sleeve according to theinvention, the valve being shown in a closed position;

. FIG. 2 is a reduced scale view on line 2-2 of FIG. 1;

FIG. 3 is a reduced scale view similar to FIG. I and showing the valvein an open position;

FIG. 3A is a view similar to FIG. 3 and showing the valve componentsjust as the valve begins to open;

FIG. 4 is a sectional elevation of another style of valve using a backupsleeve and stationary seal according to the invention;

FIG. 5 is a view on line 5-5 of FIG. 4;

FIG. 6 is a fragmentary cross-sectional elevation of the valve shown inFIG. 4 with the valve in a closed position;

FIG. 7 is a fragmentary sectional elevation of a balanced DESCRIPTION OFTHE PREFERRED EMBODIMENTS The improved seal assembly of this inventionis useful in and will be described with reference to valves whichincorporate either stationary or movably mounted resilient seals. FIGS.1-3 show a simple form of a piston valve which embodies the invention.Valve 10 includes a body member 11 having a stepped bore with a firstportion 12 and an enlarged second portion 13, the bore defining anannular shoulder 14 which separates the first and second bore portions.

A threaded opening defining a first port 16 extends through body member11 and opens into first bore portion 12. A second threaded opening 17extends transversely through the valve body member into an enlargedannular second port 18 in the second bore portion. Conventional inletand outlet lines and fittings (not shown) are connected to the threadedopenings in the valve body to conduct a fluid through the valve bore.

A valve piston or closure member 20 makes a loose slip fit in first boreportion 12 of the valve body, and has an actuating shaft 21 extendingtherefrom through a cover plate 22 which closes the end of the boreopposite first port 16. The cover plate is secured to the valve body byscrews 23, and carries an O-ring seal 24 bearing against actuating shaft21. A conventional actuating mechanism (not shown) such as a lever,handwheel, hydraulic or pneumatic cylinder, or the like, is attached tothe actuating shaft to reciprocate the closure member in the bore.Alternatively, the closure member or actuating shaft can be springloaded toward the closed position to form a pressure relief valve whichis flow actuated and does not require external actuation.

Closure member 20 has an annular groove 26 and a resilient seal 27 isseated in the groove. Seal 27 can have any of the conventional crosssections used in this type of seal, and is shown in the drawings asbeing of the usual O-ring type. When closure member 20 is in a closedposition between ports 16 and 18 as shown in FIG. 1, seal 27 bears onand is confined in groove 26 by a cylindrical inner wall 28 of the bodymember which defines first bore portion 12. Flow between the ports isthus blocked when the valve is closed by the closure member andresilient seal.

A backup sleeve 30 makes a slip fit in second bore portion 13, and hasan inwardly extending annular wall 31 at one end with an opening 32through which actuating shaft 21 of the closure member extends. Aresilient means such as a compression coil spring 33 is disposed aroundthe actuating shaft between wall 31 of the backup sleeve and cover plate22 of the valve body. The spring urges the backup sleeve to the left asseen in FIG. 1 to abut an end 34 of the sleeve against annular shoulder14 of the valve body.

The inside diameter of hollow backup sleeve 30 corresponds to the insidediameter of first bore portion 12 in the valve body. The inner wall ofthe backup sleeve thus forms a smooth extension of the first boreportion as shown in FIG. 1. End 34 of the sleeve is configured to abutand seat on annular shoulder 14 so the substantially continuous smoothsurface defined by the sleeve and wall 28 is broken only by a linecontact joint or seam between shoulder 14 and end 34.

Actuating shaft 21 is moved to the right as seen in FIG. 1 to shift theclosure member into an open position in which flow is permitted throughthe bore between ports 16 and 18. In the in- When the closure member isfully retracted into the backup sleeve, further motion of the actuatingshaft retracts both the closure member and backup sleeve away fromsecond port 18 as shown in FIG. 3. There is thus in effect a lost motioncoupling between the closure member and backup sleeve, the twocomponents being independent until the closure member is fully seatedwithin the sleeve. The sleeve and closure member can be fully retractedinto second bore portion 13 away from port 18 to open the valve to itsfullest extent (see FIG. 3), or sleeve 30 can be positioned partiallyover the second port to regulate flow through the valve to a rate lessthan the maximum flow rate.

When piston valve 10 is to be returned to a closed position, actuatingshaft 21 is moved toward port 16, and coil spring 33 returns the backupsleeve to its seated position against annular shoulder 14 while theclosure member and resilient seal are still fully retracted within thesleeve. After the sleeve has seated on the shoulder, further motion ofthe actuating shaft extends the closure member out of the backup sleeveacross the line joint between the sleeve and shoulder. When theactuating shaft is in a fully closed position as shown in FIG. 1, theresilient seal is positioned beyond this line contact joint to bearagainst and be confined by body member wall 28 which defines the firstbore portion.

The backup sleeve thus serves as a buffer member which forms a smoothextension of the first bore portion, the closure member and resilientseal being drawn into this extended bore when the valve is open. Theseal is fully isolated from the surv face discontinuity created by port18, and is continuously confined under constant squeeze in groove 26.The problems of seal extrusion are thereby avoided, and seal distortionis prevented. Pinching or cutting of the seal is also avoided as thevalve is opened and closed because the seal slides on a substantiallycontinuous smooth surface which is broken only by the line joint betweenthe backup sleeve and annular shoulder. The seal is also protected fromimpact and abrasion from the flowing fluid stream when the valve ispartially or fully open.

The concept of the invention is equally useful in valves using astationary seal, and this form of the invention is shown in piston valve40 in FIGS. 4-6. Valve 40 is a right-angle valve having a body member 41with a central chamber or cylindrical bore 42 having an axial first port43 at one end and a lateral extension 44 defining a second port 45.Annular bolt flanges 46 are provided to couple external conduits (notshown) to the valve body member.

A valve piston or'closure member 49 has a cylindrical skirt 50 making aslip fit in bore 42 of the valve body member. The leading end of theclosure member is grooved to define an annular recess 51 around itsperiphery. A closure member ac tuating shaft 52 is threaded through acover plate 53 secured by bolts 54 to an end of the valve body memberopposite first port 43. The inner end of the threaded actuating shaft iscoupled to the center of closure member 49 by a ball bearing 55 whichisolates the closure member from the rotation of the actuating shaft. Ahand wheel or power-operated shah-rotating device (not shown) isconnected to the outer end of the actuating shaft.

A conventional annular seal 57 is mounted in bore 42 of the body memberto bear against closure member 49. A pair of conventional cable springs58 separated by a continuous flat annular band 59 are positioned withinthe seal to urge the legs of the seal against the body member andclosure member. A hollow cylindrical retainer 60 forms part of the valvebody member, and is positioned between seal 57 and cover plate 53 tohold the seal in place, the inner surface of the retainer defining aportion of cylindrical bore 42. The valve is shown in a fully openposition in FIG. 4 with closure member 49 retracted into retainer 60 topermit free flow between ports 43 and 45 through the valve body.

The chamber of valve 40 is enlarged at the left end (as seen in FIG. 4)of the body member 41, and is threaded to receive a seal-retaining ring62 and a spring-retaining ring 63. The inside diameters of rings 62 and63 correspond to the inside diameter of retainer 60, and the rings thusdefine a portion of cylindrical bore 42 in which the closure membermoves to open and close the valve. An annular, generally .l-shapedresilient main seal 64 is disposed in the body member between retainingring 62 and an annular shoulder 65 on the body member. A pair of flatwire helical cable springs 66 are positioned between ring 62 and seal 64on opposite sides of an axially extending annular rib 67 on ring 62. Theouter spring 66 urges seal 64 against shoulder 65, and the inner springurges the seal radially inwardly toward the axis of cylindrical bore 42.

A backup element or sleeve 70 makes a slip fit in bore 42 against rings62 and 63, and against body member 41 adjacent shoulder 65. The backupsleeve has an outwardly extending annular flange 71 secured theretowhich abuts ring 62 to limit the inward travel (to the right in FIG. 4)of the backup sleeve. A plurality of compression coil springs 72 areseated in circular recesses 73 and 74 in rings 62 and 63 respectively,and the springs urge flange 71 against ring 62 to position the backupsleeve as shown in FIG. 4. A key 76 is secured to the backup sleeve andmates with a longitudinally extending slot 77 (see FIG. 5) to preventrotation of the sleeve which might tend to unseat springs 72.

With closure member 49 positioned as shown in FIG. 4, the valve is fullyopen and fluid can flow freely between ports 43 and 45. SEal 57 preventsleakage of fluid past the retracted closure member when the valve isopen. To close the valve, actuating shaft 52 is rotated to drive theclosure member across second port 45 to a closed position as shown inFIG. 6. When the valve is closed, resilient main seal 64 bears on theperiphery of the closure member to prevent fluid leakage between thevalve body member and closure member.

As the closure member is being moved toward the fully closed position,the inner end of backup sleeve 70 seats in annular recess 51 of theclosure member, and the sleeve forms a smooth extension of the closuremember surface, the total surface being broken only by the line jointbetween the sleeve and closure member. Continued motion of the closuremember toward the fully closed position (to the left in FIGS. 4 and 6)moves the backup sleeve across resilient seal 64 toward the positionshown in FIG. 6. The seal is continuously confined by the backup sleeveand closure member in the annular space defined by the seal-retainingring 62 and shoulder 65, and is thereby prevented form extruding intothe cylindrical bore of the valve. Pinchirrg or cutting of the seal isalso avoided as the line contact joint between the closure member andbackup sleeve passes smoothly over the seal as the valve is closed.

When the valve is opened by rotating actuating shaft 52 to retract theclosure member, springs 72 force the backup sleeve to slide over seal 64and to follow the closure member until flange 71 abuts ring 62.Continued retraction of the clo sure member then opens the valve topermit flow between the ports. The seal is thus continuously supportedand confined for any position of the closure member, and is protectedfrom abrasion or tearing.

The seal structure just described with reference to valve 40 is shown inanother form in FIG. 7 which illustrates a threeport fully balancedspool valve 80. The valve includes a body member 81 having a cylindricalbore 82 therethrough. An inlet port 83 opens laterally into the bore,and a pair of longitudinally spaced outlet ports 84 open into the boreacross from and on opposite sides of the inlet port.

A piston assembly 86 is slidably mounted in the bore, and includes acentral flow control closure member 87 and a pair of force-balancingpistons 88 connected to opposite sides of the closure member by a pairof shafts 89. A control shaft 90 extends out of the valve to anactuating mechanism (not shown) which reciprocates the closure member inthe bore to permit flow between the inlet port and either one of theoutlet ports.

A pair of O-ring resilient seals 92 are mounted in annular port 83. Theseals close the annular clearance space between the body member andclosure member 87 when the piston assembly is in a closed position asshown in FIG. 7. A pair of backup elements or sleeves 94 are positionedon opposite sides of the closure member and make a slip fit in bore 82.

The end of each backup sleeve 94remote from the closure member defines aradially outwardly extending flange 95. Bore 82 is enlarged in diameteradjacent each of the outlet ports to make a slip fit over flanges 95,and to define an annular shoulder 96 between each seal 92 the outletports. The ends of the enlarged portions of the bore remote from theclosure member also define annular shoulders 97.

A pair of compression coil springs98 are positioned in the enlargedportions of the body member bore between shoulders 97 and flanges on thebackup sleeves. The ends of the closure member are slightly reduced indiameter to fit within the ends of the backup sleeves so the sleevesabut the closure member and only line joints appear in the combinedperipheral surfaces of the abutted components. Springs 98 urge thebackup sleeves against the closure member as shown in FIG. 7. Eachsleeve is free to move with the closure member away from the inlet portagainst the force of the associated coil spring, and can also movetoward the inlet port to cover seal 92 when flange 95 abuts shoulder 96.

In operation, piston assembly 86 is moved to the left or right as seenin FIG. 7 to permit flow between the inlet port and the one of theoutlet ports. As the closure member is moved away from the inlet port,one of the backup sleeves follows the closure member to confine andcover the resilient seal which would otherwise be exposed by theretracting piston. Extrusion of the seal is thereby prevented, andabrasion or pinching is also avoided as the seal sees" no more than theline joint between the backup sleeve and closure member.

The invention is not limited to, piston-type valves, and is equallyuseful in a guillotine-type sliding gate valve 100 as shown in FIGS.8-10. This valve has a body member 101 with a chamber-defining slot 102and a pair of ports 103 extending through the body member intocommunication with the slot. A valve gate or closure member 104 isslidably mounted in slot 102 to seal the ports from each other when thevalve is in a closed position as shown in FIG. 8. Leakage is preventedby a resilient seal 105 seated in a generally rectangular groove 106 inthe closure member and bearing against the opposed sur face of the bodymember.

Slot 102 in the body member is increased in width adjacent one of theports to define a rectangular channel 108, and a backup element or plate109 is slidably mounted in this channel between the closure member andbody member. The backup plate has a lug or flange 110 extending from oneside thereof into an elongated channel 111 formed in a face of theclosure member opposite channel 108; A resilient member such as a wavespring 112 is disposed in channel 108 to act against the backup plateand urge it across the adjacent port to seat on a shoulder 113 in theend of channel 108.

When the valve is opened by raisingclosure member 104 to permit flowbetween the ports, resilient seal 105 passes smoothly over the linejoint defined by the abutted backup plate and shoulder 113. Thesurface-of the backup plate thus forms a smooth, substantiallycontinuous extension of the slot surface against which the closuremember and seal bear. As the closure member is raised, flange 1l0isengaged by the bottom of channel 111 and the backup plate is thereafterraised with the closure member until the valve is fully open as shown inFIG. 10.

When the valve is returned to a closed position, the backup plate againseats in the position shown in FIG. 8 before the gate reaches the bottomof the slot."Ihe seal is thus continuously confined and supported byeither the backup plate or the slot-defining surface of the body member,and extrusion or abrasion of the seal is avoided as explained above. Theinvention can of course also be adapted to a gate valve using astagrooves 93 in the valve body member on opposite sides of inlet 75tionary seal mounted in the valve body member.

A moving seal plug valve 120 incorporating the invention is shown inFIGS. 11-12. The plug valve has a body member 121 with a cylindricalbore 122, and a pair of ports 123 and 124 extend through the body memberinto the bore. A cylindrical plug or valve closure member 125 makes arotating slip fit within bore 122, and is held within the body member bya cover plate 126. A valve control shaft 127 is secured to and extendsupwardly from the closure member through cover plate 126. A pair ofconventional O-ring seals 128 are disposed in grooves 129 in the coverplate to prevent leakage between the cover plate, control shaft and bodymember.

A central portion 130 of closure member l25'is cut away to have a crosssection in the shape of a circular segment as shown in FIG. 12. Theclosure member is shown in a closed position in FIG. 12, but can berotated away from this position to permit unobstructed flow through thevalve between the ports. The closure member is shown in phantom line inFIG. 12 to indicate its open position. A stop 131 extends into bore 122from the body member to limit the travel of the closure member in theclosed position.

Bore 122 in the body member is enlarged on opposite sides of port 124 todefine a curved channel 133 opposite central portion 130 of the closuremember. A curved backup element or plate 134 shaped as an annularsegment is slidably mounted in channel 133 to extend over port 124 whenthe valve is closed as shown in FIG. 12. A lug 135 extends inwardly fromhe backup plate into a channel 136 in central portion 130 of the closuremember. A spring 137 is mounted in channel 133 to urge the backup plateinto a seated position as shown in FIG. 12.

A resilient seal I39 is seated in a groove 140 in the face of theclosure member, and bears against the body member around port 124 andchannel 133 to prevent leakage between the closure member and bodymember when the valve is in a closed position. When the valve is opened,seal 139 moves smoothly over the line joint between the body member andbackup plate 134. Continued rotation of the closure member causes theend of channel 136 to engage lug 135 and rotate the backup plate awayfrom port 124 into the opposite end of channell33. Free flow through thevalve between the ports is then permitted.

The opposite sequence occurs when the valve is closed, the backup platebeing returned to its seated position by spring 137 before seal 139passes off of the backup plate onto the body member. The seal is thuscontinuously confined and supported by the backup plate and body memberwhich cooperate to define a smooth and substantially continuous surfacebearing against the seal.

The invention is equally applicable to a plug valve 150 with astationary sea] as shown in FIG. 13. This valve is generally similar tovalve 120 just described in that it has a body member 151 with acylindrical bore 152 and a pair of opposed ports 153 and 154 extendingthrough the body member into the bore. A cylindrical plug closure member155 with a cutaway sector-shaped central portion 156 is fitted in thebore to be rotatable between closed and open positions as shown in solidand phantom lines respectively in FIG. 13.

A stationary resilient seal 159 is mounted in a groove 160 in the bodymember to bear against the central portion of the closure member toprevent leakage when the valve is closed. The cylindrical portions ofthe closure member above and below the sector-shaped central portiondefine a channel 162 in which a curved backup plate 163 is slidablymounted, the plate being shaped as an annular segment. A lug 164 extendsoutwardly from the backup plate into a groove 165 in the body member. Aresilient means such as a leaf spring 166 or any other conventionalspring is disposed between the body member and backup plate to urge thebackup plate against the closure member in a seated position as shown inFIG. 13.

When the closure member is rotated into the open position, spring 166forces "thebackup plate to follow the closure member until the backupplate has covered seal 159, and lug the closure member then places thevalve in a fully open position in which fluid flows freely through thevalve between the ports. As in the other types of vdves described above,the resilient sleeve is continuously supported and confined by eitherthe backup plate or the closure member, and extrusion of the seal isthereby prevented. The backup plate and closure member cooperate todefine a smooth and substantially continuous surface or shield bearingagainst the seal and broken only by the line joint between thesecomponents.

The invention has been described with reference to several differentstyles of valves to show thait is useful in many different types of sealapplications in which seal extrusion, distortion, abrasion and pinchingare a problem. The invention finds particular utility in high-pressurevalves, or in valves handling low-temperature fluids which tend toharden a resilient seal and make it more vulnerable to chipping orbreakage. The invention, however, is not limited to these specificapplications, and is useful in any device employing a resilient sealwhich is to be protected against extrusion and other damage.

For example, the invention is well suited for use in pressure reliefvalves which may be of the flow-actuated type. The invention isespecially valuable in controlling flow of abrasive seal-eroding fluidsbecause the seal is isolated from the flowing fluid stream. Similarly,the seal is protected from the highvelocity fluid stream which canquickly erode a soft seal in a high-pressure valve, or in lower pmureapplications where the valve is only slightly opened in a meteringposition. Secondary hydraulic systems used to handle leakage flow inconventional valves are also eliminated by the improved seal-protectingconfiguration.

The invention has been illustrated in terms of various valves having abackup member which is spring urged toward a seated position, but otherarrangements are practical and feasible. For example, the backup membercan be coupled to an external actuator which is timed or synchronized tomaintain a proper relationship between theseal, closure member andbackup element for any valve This arrangement is especially suitable forlarge valves which are positioned by power actuators rather thanhandwheels or levers. Other variations and applications of the basicimprovement will suggest themselves to those concerned with themaintenance of a high-integrity seal between relatively movable members.

What is claimed is: l

1. An improved gate valve, comprising:

a valve body member having a slot therein defining a chamber, and a pairof spaced-apart aligned ports opening into opposite sides of thechamber;

a plate forming a closure gate member disposed in the chamber to belinearly slidable in the slot between an open position in which a fluidcan flow through the chamber between the ports and a closed position inwhich the closure member is disposed between the ports to block flowtherebetween, the closure member being slidable transversely withrespect to a direction of flow between the ports when the valve is open;

a resilient seal mounted on orient the members to be in sliding contactwith the other member as the closure member is moved away from theclosed position, the seal being confined between the members to seal thevalve when the closure member is in the closed position; and

a backup element slidably disposed in the chamber and arranged to moveinto abutment with said other member as the closure member is movedtoward the closed position, the backup element being configured todefine in conjunction with said other member a substantially continuoussmooth surface in sliding contact with the seal and against which theseal is compressed as the closure member is moved from the closedposition toward the open position. l

2. The gate valve defined in claim 1 and further comprising resilientmeans arranged to urge the backup element toward a position in whichsaid substantially continuous smooth surface 164 has abutted the end ofgroove 165. Continued rotation of is defined.

1. An improved gate valve, comprising: a valve body member having a slottherein defining a chamber, and a pair of spaced-apart aligned portsopening into opposite sides of the chamber; a plate forming a closuregate member disposed in the chamber to be linearly slidable in the slotbetween an open position in which a fluid can flow through the chamberbetween the ports and a closed position in which the closure member isdisposed between the ports to block flow therebetween, the closuremember being slidable transversely with respect to a direction of flowbetween the ports when the valve is open; a resilient seal mounted onone of the members to be in sliding contact with the other member as theclosure member is moved away from the closed position, the seal beingconfined between the members to seal the valve when the closure memberis in the closed position; and a backup element slidably disposed in thechamber and arranged to move into abutment with said other member as theclosure member is moved toward the closed position, the backup elementbeing configured to define in conjunction with said other member asubstantially continuous smooth surface in sliding contact with the sealand against which the seal is compressed as the closure member is movedfrom the closed position toward the open position.
 2. The gate valvedefined in claim 1 and further comprising resilient means arranged tourge the backup element toward a position in which said substantiallycontinuous smooth surface is defined.
 3. The gate valve defined in claim2 in which the backup element is a plate slidably fitted in a channel insaid other member, the plate having a lug extending therefrom to engagesaid one member and thereby move the backup element plate as the valveis opened, the resilient seal extending around the backup element plateand associated resilient means when the valve is closed.